On 5/30/2022 10:24 PM, Vinod Koul wrote:
On 30-05-22, 10:06, Geert Uytterhoeven wrote:
Hi Dave, Vinod,
Hi Geert,
On Wed, Apr 13, 2022 at 12:58 AM Dave Jiang <dave.jiang@xxxxxxxxx> wrote:
Looks like I forgot to add DMA_INTERRUPT cap setting to the idxd driver and
dmatest is still working regardless of this mistake. Add an explicit check
of DMA_INTERRUPT capability for dmatest to make sure the DMA device being used
actually supports interrupt before the test is launched and also that the
driver is programmed correctly.
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Thanks for your patch, which is now commit a8facc7b988599f8
("dmaengine: add verification of DMA_INTERRUPT capability for
dmatest") upstream.
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -675,10 +675,16 @@ static int dmatest_func(void *data)
/*
* src and dst buffers are freed by ourselves below
*/
- if (params->polled)
+ if (params->polled) {
flags = DMA_CTRL_ACK;
- else
- flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
+ } else {
+ if (dma_has_cap(DMA_INTERRUPT, dev->cap_mask)) {
+ flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
+ } else {
+ pr_err("Channel does not support interrupt!\n");
+ goto err_pq_array;
+ }
+ }
ktime = ktime_get();
while (!(kthread_should_stop() ||
@@ -906,6 +912,7 @@ static int dmatest_func(void *data)
Shimoda-san reports that this commit breaks dmatest on rcar-dmac.
Like most DMA engine drivers, rcar-dmac does not set the DMA_INTERRUPT
capability flag, hence dmatest now fails to start:
dmatest: Channel does not support interrupt!
To me, it looks like the new check is bogus, as I believe it confuses
two different concepts:
1. Documentation/driver-api/dmaengine/provider.rst says:
- DMA_INTERRUPT
- The device is able to trigger a dummy transfer that will
generate periodic interrupts
2. In non-polled mode, dmatest sets DMA_PREP_INTERRUPT.
include/linux/dmaengine.h says:
* @DMA_PREP_INTERRUPT - trigger an interrupt (callback) upon
completion of
* this transaction
As dmatest uses real transfers, I think it does not depend on
the ability to use interrupts from dummy transfers.
Yes this does not look right to me. DMA_INTERRUPT is for a specific
capability which is linked to dma_prep_interrupt() which dmatest does
not use so i think it is not correct for dmatest to use this...
I can revert this patch... Dave?
Yes we can revert it.
